Cannon wanted to make sure that Bynes knew he was only a phone call away, if she ever needed it.

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Nick Cannon arrives at the LA premiere of "Kevin Hart: Let Me Explain" at the Regal Cinemas at L.A. Live on Thursday, June 27, 2013 in Los Angeles. Cannon shared his concern for his "little sister" Amanda Bynes in an open letter to the troubled star.

"As of lately I have been hit with an onslaught of questions about someone I consider family, someone I watched grow up, and someone I genuinely feel is one of the most pleasant human beings I have had the pleasure of meeting, Amanda Bynes," Cannon said.

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Mariah Carey's hubby continued to say that although "fame and entertainment is one of the best and easiest occupations to ever have," it can also swallow a person up if they don't know how to navigate through, what he calls, the "matrix."

"I've seen it happen to many of my friends and colleagues young and old. It goes back to that old saying; 'Too much of anything is bad for anyone.' Whether it's fame, money, sex, drugs, attention. It's all a dangerous addiction," Cannon wrote.

"We all end up alone in that dark hole at some point in our lives and if you don't have a foundation of friends and family to help bring you up and out it makes that journey long and detrimental."

Nick wanted to make sure that Bynes knew he was only a phone call away, if she ever needed it.

"So I say to my sister Amanda Bynes you're not alone. I'm here for you. I understand. I care and I appreciate you, because that's what family does and that's what family is for."

Last week, E! News confirmed that Bynes was detained by police and taken into custody for a mental health evaluation after being "involved in a disturbance in a residential neighborhood," and ultimately placed on a 5150 hold.